Intraoperative hypotension and postoperative acute kidney injury in patients undergoing prolonged intra-abdominal surgery: a retrospective, observational study

Abstract Background Intraoperative hypotension may be associated with postoperative acute kidney injury (AKI). However, patients undergoing prolonged intra-abdominal surgery may be susceptible to postoperative AKI due to procedure-related physiological changes. Therefore, this study aimed to investigate the association between intraoperative hypotension and the incidence of postoperative AKI in patients undergoing prolonged intra-abdominal surgery with a potentially increased risk of postoperative AKI. Methods This retrospective, observational study included 269 adult patients who underwent intra-abdominal surgery, with American Society of Anesthesiologists Physical Status (ASA-PS) II–IV, anesthesia duration ≥ 300 min, and preoperative serum creatinine ≥ 0.8 mg/dL. The primary outcome was AKI within the first 7 postoperative days. The associations of intraoperative mean arterial pressure (MAP) less than 55, 60, and 65 mmHg with postoperative AKI were investigated. Multivariable regression models were used to adjust for potential confounding variables. Results Postoperative AKI occurred in 15 (5.6%) patients. Patients with AKI had longer cumulative durations of intraoperative hypotension defined as MAP < 65 mmHg (103 vs. 46 min, p = 0.031) and < 60 mmHg (24 vs. 11 min, p = 0.035). On multivariable analysis, lower intraoperative urine output was associated with postoperative AKI (adjusted odds ratio 0.226; 95% confidence interval 0.058–0.890, p = 0.033), whereas the association between the cumulative duration of MAP < 65 mmHg and postoperative AKI was no longer statistically significant (adjusted OR 1.054 per 10 min; 95% CI 0.994–1.112; p = 0.076). Conclusion Intraoperative hypotension was common in patients undergoing prolonged intra-abdominal surgery. Although patients who developed AKI experienced longer cumulative durations of intraoperative hypotension in the unadjusted analysis, an association between intraoperative MAP < 65 mmHg and postoperative AKI was not demonstrated in the multivariable analysis. Lower intraoperative urine output was associated with postoperative AKI. These findings are exploratory and hypothesis-generating.